Microalgae are proving to be of great utility because they present a large number of beneficial applications in various different areas, such as wastewater treatment, production of biofuels, food for humans and animals, and the obtainment of high-value chemical products. Microalgae cultures may reach productivities that are much higher than those of traditional cultures, leading to a greater CO2 fixation and a larger quantity of biomass produced. Moreover, microalgae cultures have lower water requirements and do not compete with traditional cultures, since they do not need fertile soil or potable water.
In order to obtain an optimal profitability in large-scale microalgae production projects, large areas, in addition to sufficiently large industrial facilities, are needed in order to justify the necessary investments. Microalgae production systems primarily include two differentiated classes: closed systems and open systems. Closed systems are characterised in that they insulate the fluid from the external environment and are less exposed to disturbances, whereas open systems are characterised in that they have a greater interaction with or exposure to the environment and are more dependent on the conditions thereof.
Microalgae production systems are equipped with devices designed to extract the microalgae once they are generated; this is what is called “harvesting”. They are also equipped with devices designed for the inclusion of new culture media, where culture medium is understood to mean the set of nutrients dissolved in water which the microalgae need, as well as for the stirring and reduction of concentration gradients, the elimination of oxygen and the absorption of carbon dioxide in the culture medium.
In microalgae production systems, the following factors must be taken into consideration in order to achieve the maximum yield:                Oxygen at high concentrations may be toxic for the microalgae, especially when there is a high solar radiation,        Microalgae perform photosynthesis and, therefore, should have sufficient light available, although an excess of light may be harmful. Microalgae should not remain in permanent darkness, and an optimal light exposure frequency makes it possible to optimise the productivity,        The nutrients supplied should be homogenised, such that the microalgae may grow in all the areas of the system,        The CO2 should be distributed throughout the entire culture system, such that the microalgae may fixate this CO2,        The decanting of microalgae in dead zones of the culture systems should be avoided, since, in addition to entailing a loss of productivity, because these cells do not have access to light, the decanted cells may be a contamination focus,        The culture systems should be kept clean, in order to prevent contaminations that may affect the growth of the microalgae,        The microalgae cultures should be kept within an appropriate temperature range, in order to optimise the productivity and prevent cell death caused by cold or excessive heat.        
The microalgae culture systems known by the applicant are either tubular systems that may be closed or large bags, preferably made of a plastic material, which present a high energy consumption to obtain an acceptable yield in microalgae production.